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## Circumference

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**Circumference**By Maria Bocanegra**What is circumference?**• The distance around aclosed curved circle.**Circumference of a circle**• Circumference of acircle is the length around it. It • can be calculated from its diameter using this formula: • Circumference = π × diameter • Circumference • Diameter**The first two steps**• 2. Radius: it is the distance from the center of a circle. It is half its diameter. When the diameter is too large to determine, estimate the radius then use simple math and multiply the radius by 2. • Radius • 1. Diameter: you need to measure the diameter. The diameter is the distance that’s across a circle through its center. It is visualized as a straight line cutting the circle. • Diameter**Next Two Steps**• 4. How to calculate circumference: you use simple math to multiply the diameter by pi. If a jogger estimated the diameter of a circular path as 200 meters across, then the circumference would be: • 200 X 3.14 = • 628 meters • 3. Grasp Pi: it is the ratio of the circumference to its diameter. Pi is called Constant Math. It is a number that does not change, no matter the size of the circle. Pi is usually rounded to 3.14. • Symbol for Pi**Last Step**• 5. Verify the units of measurement. The measurements for circumference are the same as the units for the diameter. If the diameter is measured in meters then you should report the circumference in meters. • The diameter d is the distance across a circle through its center. • The circumference c is the distance around a circle. • The radius r is the distance from the center to any point of the circle. • The circumference c is equal to its diameter d X pi, or two X radius rXpi.**First example**• What is the circumference of a circle with a radius (r) of 4cm? • Diameter of a circle = 2 X r • Circumference of a circle = d X pi • 8 X pi • 8 X 3.14 = 25.12**Second EXAMPLE**• What is the circumference of a circle with a radius (r) of 12cm? • Diameter of a circle = 2 X r • Circumference of a circle = d X pi • 24 X pi • 24 X 3.14 = 75.36**THIRD EXAMPLE**• What is the circumference of a circle with a radius (r) of 3cm? • Diameter of a circle = 2 X r • Circumference of a circle = d X pi • 6 X pi • 6 X 3.14 = 18.84